This invention relates to a process and apparatus for pneumatically conveying particulate material from one location to another and is particularly concerned with a process and apparatus for feeding coal, oil shale and similar carbonaceous solids which tend to agglomerate and/or swell to a processing vessel operated at an elevated temperature.
Pneumatic conveying systems are utilized widely throughout industry for transporting particulate materials from one place to another. For example, industrial pneumatic conveying systems are used to transport flour, seeds, grains, and powdered bulk materials in enclosed pipeline systems from one portion of a processing plant to another. Pneumatic conveying can also be used to pass such particulate solids from storage vessels into reactors operated at high pressures and temperatures. However, the application of such pneumatic conveying techniques to transport coal, oil shale and other carbonaceous solids containing volatilizable hydrocarbons from storage facilities into reactors or other processing vessels operated at elevated temperatures has generally been unsuccessful. As the carbonaceous solids flow through a conveying tube to the reactor, the temperature to which they are subjected increases rather rapidly causing the solids to swell and become sticky. This, in turn, normally leads to the formation of agglomerates in the tube which ultimately results in bridging of the feed solids and interruption of the normal flow of feed to the reaction vessel. In severe cases, large agglomerates form and block the entire feed line thereby resulting in a complete shut-down of the process.